There was a period of cold temperatures--referred to as 'the little ice age'--in the mid 17th century.  At the same time, the sun had became exceptionally quiet in terms of sunspot activity. Known as the "Maunder Minimum", the number of sunspots observed over a 70-year period were reduced by three orders of magnitude. 
Now we are again observing what may become a protracted quiet period for the sun. In May, 2006, sunspot activity had fallen to a exceptionally low level.  This period, marked by sporadic or no activity, has persisted into April of this year. [3, 4, 5]
So, with the current solar cycle off to a slow start and the next cycle forecasted to be weaker yet  , it seems the prudent course of action vis-a-vis global warming is to sit tight and do nothing rash.